Do you have multiple WiFi bands? Does the problem occur on all bands? I would try “forgetting” the network and try entering the credentials again. I know you said it’s new but one of my older Roku devices could only connect to my newer WiFi node and not the main router so it actually connects to the farther node on the mesh. I could never figure it out even though they had the same login credentials and passwords and on the same bands.
Do you rent the whole house or are the landlords also living there? If you occupy the whole space you may want to look into Moca, you get the Ethernet from your router the adapter changes the signal to coax, you feed it back into the wall and you have another adapter where you the Ethernet (the bedroom). You do need coax outlets in both places and you may need specific moca splitters and it may not work well if you’re also using the coax for satellite but it’s been great for me (we gave up coax tv a while ago so all the coax cables throughout the house are used to convert internet to Ethernet on the other side of the house and the spare bedroom. It’s worked very reliably). I ask if you rent the whole house because if you feed your internet into the house coax, your landlord could also potentially pick up that signal through the coax on their side.
My guess is your building is probably all fed into a single box or source somewhere.
MOCA does have some information in regards to building type arrangements but forewarning I use moca in a single family type arrangement and not and apartment and I don’t know exactly what the parameters would be. I would think in this instance it would be on a building wide type of arrangement and not individual units. If the cable was direct from end to end in your unit without feeding other units I would say without hesitation it would work great.
https://mocalliance.org/access/index.php